In recent years, electrochemical elements, especially lithium secondary batteries have been widely used as power supplies for small-sized electronic devices such as mobile telephones, notebook-size personal computers and the like, power supplies for electric vehicles, as well as for electric power storage. These electronic devices and vehicles may be used in a broad temperature range, for example, at midsummer high temperatures or at frigid low temperatures, and are therefore required to be improved in point of the discharge capacity in a broad temperature range even after long-term use.
In this specification, the term of lithium secondary battery is used as a concept including so-called lithium ion secondary batteries.
The lithium secondary battery is mainly constituted of a positive electrode and a negative electrode containing a material capable of absorbing and releasing lithium, and a nonaqueous electrolytic solution containing a lithium salt and a nonaqueous solvent. For the nonaqueous solvent, used are carbonates such as ethylene carbonate (EC), propylene carbonate (PC), etc.
As the negative electrode, known are metal lithium, and metal compounds (metal elemental substances, oxides, alloys with lithium, etc.) and carbon materials capable of absorbing and releasing lithium. In particular, a lithium secondary battery using a carbon material capable of absorbing and releasing lithium, such as coke, artificial graphite, natural graphite or the like, has been widely put into practical use.
For example, it is known that, in a lithium secondary battery using a highly-crystalline carbon material such as natural graphite, artificial graphite or the like as the negative electrode material therein, the decomposed product or gas generated through reductive decomposition of the solvent in the nonaqueous electrolytic solution on the surface of the negative electrode during charging detracts from the electrochemical reaction favorable for the battery, therefore worsening the cycle properties of the battery. Deposition of the decomposed product of the nonaqueous solvent interferes with smooth absorption and release of lithium by the negative electrode, and therefore, in particular, the cycle properties at low temperatures and at high temperatures may be thereby often worsened.
In addition, it is known that a lithium secondary battery using a lithium metal or its alloy, or a metal elemental substance such as tin, silicon or the like or its metal oxide as the negative electrode material therein may have a high initial battery capacity but its battery performance such as battery capacity and cycle properties greatly worsens, since the micronized powdering of the material is promoted during cycles thereby bringing about accelerated reductive decomposition of the nonaqueous solvent, as compared with the negative electrode of a carbon material. In addition, the micronized powdering of the negative electrode material and the deposition of the decomposed product of the nonaqueous solvent may interfere with smooth absorption and release of lithium by the negative electrode, and therefore, in particular, the cycle properties at low temperatures and at high temperatures may be thereby often worsened.
On the other hand, it is known that, in a lithium secondary battery using, for example, LiCoO2, LiMn2O4, LiNiO2, LiFePO4 or the like as the positive electrode, when the nonaqueous solvent in the nonaqueous electrolytic solution is heated at a high temperature in the charged state, the decomposed product or the gas thereby locally generated through partial oxidative decomposition in the interface between the positive electrode material and the nonaqueous electrolytic solution interferes with the electrochemical reaction favorable for the battery, and therefore the battery performance such as cycle properties and others are thereby also worsened.
As in the above, the decomposed product and the gas generated through decomposition of the nonaqueous electrolytic solution on the positive electrode or the negative electrode may interfere with the movement of lithium ions or may swell the battery, and the battery performance is thereby worsened. Despite the situation, electronic appliances equipped with lithium secondary batteries therein are offering more and more an increasing range of functions and are being in a stream of further increase in the power consumption. With that, the capacity of lithium secondary batteries is being much increased, and the space volume for the nonaqueous electrolytic solution in the battery is decreased by increasing the density of the electrode and by reducing the useless space volume in the battery. Accordingly, the situation is that even decomposition of only a small amount of the nonaqueous electrolytic solution may worsen the battery performance at low temperatures and at high temperatures.
Patent Reference 1 discloses a lithium ion secondary battery that comprises a positive electrode containing a lithium manganese oxide having a spinel structure, a negative electrode containing a carbon material and an organic electrolytic solution, wherein the organic electrolytic solution contains a malonic diester in an amount of from 0.5 to 3.0%, saying that the cycle properties of the battery at 25° C. are thereby enhanced.
Patent Reference 2 discloses an electrolytic solution with a silyl carboxylate such as trimethylsilyl trimethylsilyloxyacetate or the like added thereto. This shows that the hydroxy acid derivative compound of that type in which both the hydrogen atoms of the hydroxyl group and the carboxyl group of the hydroxy acid each are substituted with an alkylsilyl group forms a “tough modified” SEI film (surface film) on the carbon electrode surface of the anode (negative electrode), thereby enhancing the cycle properties of the battery having a silicon thin film as the negative electrode.
Patent Reference 3 discloses a lithium ion secondary battery in which an oxygen-containing aliphatic compound having an alkynyl group and/or an alkynylene group with no active hydrogen is added to the nonaqueous electrolytic solution, saying that the cycle properties at 20° C. and 60° C. of the battery can be improved.
Patent Reference 4 discloses an electrolytic solution containing a dialkyl ester compound such as dimethyl succinate in an amount of from 10 to 30% by volume in a nonaqueous solvent, showing excellent high-temperature storage properties and cycle properties.
As a lithium primary battery, for example, known is one in which the positive electrode is formed of manganese dioxide or fluorographite and the negative electrode is formed of lithium metal, and the lithium primary battery of the type is widely used as having a high energy density, for which, however, it is desired to prevent the increase in the internal resistance during long term storage and to enhance the discharge load characteristic at high temperatures and at low temperatures.
Recently, further, as a novel power source for electric vehicles or hybrid electric vehicles, electric storage devices have been developed, for example, an electric double layer capacitor using activated carbon or the like as the electrode from the viewpoint of the output density thereof, and a hybrid capacitor including a combination of the electric storage principle of a lithium ion secondary battery and that of an electric double layer capacitor (an asymmetric capacitor where both the capacity by lithium absorption and release and the electric double layer capacity are utilized) from the viewpoint of both the energy density and the output density thereof; and it is desired to improve the properties such as the cycle properties at high temperatures and at low temperatures of these capacitors.    [Patent Reference 1] JP-A 2000-223153    [Patent Reference 2] JP-A 2006-351535    [Patent Reference 3] JP-A 2001-256995    [Patent Reference 4] JP-A 7-272756